In a current wireless communications system, a time division duplex technology or a frequency division duplex technology is used to implement bidirectional communication. In a time division duplex communications system, data is transmitted by using a same frequency but in different timeslots, which effectively isolates interference between uplink and downlink; in a frequency division duplex communications system, data is transmitted in a same timeslot but by using different frequencies, which effectively isolates interference between uplink and downlink. It may be learned that, in the time division duplex communications system, a time domain resource of a radio spectrum is sacrificed, and in the frequency division duplex communications system, a frequency domain resource of a radio spectrum is sacrificed, which causes relatively low resource usage of the radio spectrum.
As wireless data services increase day by day, a spatial radio channel becomes increasingly congested. In this case, a co-frequency co-time full duplex (CCFD) system is proposed, where in the co-frequency co-time full duplex system, uplink and downlink data can be transmitted in a same timeslot and in a same frequency, thereby improving resource usage of the radio spectrum.
However, in the co-frequency co-time full duplex system, a wireless device has both a receive end function and a transmit end function; and signal receiving and signal sending are performed at a same time and in a same frequency. Therefore, a first signal generated by the wireless device itself causes, on a radio channel, interference to a second signal sent by an external device and received by the wireless device used as a received end. The interference is referred to as self-interference, and the first signal is also referred to as a self-interference signal.
Due to a location relationship between receive and transmit antennas in the wireless device, interference strength of the self-interference signal is far higher than signal strength of the second signal sent by the external device and received by the wireless device. Therefore, in the co-frequency co-time full duplex system, the interference strength generated by the self-interference signal greatly affects the second signal sent by the external device and received by the wireless device, thereby deteriorating communication performance of the wireless device.
To improve the communication performance of the co-frequency co-time full duplex system, and effectively eliminate interference generated by the self-interference signal, a digital self-interference suppressing method, an analog self-interference suppressing method, an antenna self-interference suppressing method, and the like are proposed. In addition, a self-interference channel estimation technology is a key factor that affects a self-interference suppressing technology.
However, currently used self-interference channel estimation methods mainly include two types: One type is a channel estimation method based on adaptive filtering; the other type is a channel estimation method based on a pilot. However, in a practical application process, during self-interference channel estimation by means of the two types of methods, once the wireless device receives the second signal sent by the external device, which means that a wanted signal appears in the system, precision of self-interference channel estimation declines, which leads to performance deterioration of self-interference channel estimation.